A gouge scarred the top of the Airbus 380's left wing, scorch marks were on the outside of the blown-out engine and part of its cover depicting the airline's familiar red kangaroo logo had fallen off during the flight over Indonesia.

After a tense 95 minutes while the pilots dumped fuel, the massive, double-decker plane - the world's largest - returned safely Thursday to Singapore, where it made an emergency landing with 459 people aboard.

Qantas and Singapore Airlines grounded their Airbus A380 jetliners after Rolls-Royce, which manufactured the engines, recommended a series of checks.

Lufthansa grounded its A380 scheduled to depart Frankfurt for Johannesburg while it checked the engines, and instead used an A340-600 on the route, spokesman Boris Ogursky said. Lufthansa plans to fly the A380 from Frankfurt to Tokyo as scheduled on Friday, he added.

The failure of the No. 2 engine - one of four on the jet - was the most serious in-flight incident involving the A380 since it debuted in 2007 with Singapore Airlines flying it to Sydney. That's the same route that Thursday's Qantas Flight QF34 was making.

Passengers praised the Qantas crew for their reassuring announcements.

"Panic would have broken out, but the crew kept people updated and were behaving as if it (the situation) was so trivial," said Matthew Hewitt, a 25-year-old engineer from Manchester in Britain. "The crew was so calm."

Experts said the problem appeared to be an "uncontained engine failure," which occurs when turbine debris punctures the engine casing and the light cowling that covers the unit.

Qantas CEO Alan Joyce appeared to blame the engines, made by Rolls-Royce.

"This issue, an engine failure, has been one that we haven't seen before. So we are obviously taking it very seriously because it is a significant engine failure," he told a Sydney news conference where he announced Qantas was grounding its six A380s.

The risk isn't so much from the loss of engine power because the A380 had three other engines to rely on, said former National Transportation Safety Board member John Goglia. Rather, the concern is that hot metal parts could shoot out from the engine much like shrapnel and pierce the fuselage, perhaps leading to rapid depressurization, or puncture fuel lines in the wings, possibly starting a fire, he said.

The damage on the upper side of the left wing appeared to be just behind its leading edge, an area that is actually hollow and abuts the landing-gear bay.

"The tanks are located and designed to be protected in case of such problems. The wing was affected, but absolutely not the fuel tank," said Airbus spokeswoman Aude Lebas.

Such engine failures, which have become very rare in both civil and military aviation, are not considered particularly worrying. Statistics show these occur about once in a million flights, although this was the first major safety incident involving the A380.

"All engine failures are really becoming increasingly rare because reliability has increased dramatically in last 20 years," said William Voss, president of the Flight Safety Foundation in Alexandria, Va.

"It's particularly rare to have an uncontained engine failure," he said.

The Australian Transport Safety Bureau sent four investigators to Singapore. Airbus said it was providing all necessary technical assistance to the probe and a team of specialists was being dispatched to Singapore.

The most frequent causes of engines failures are the ingestion of loose objects on the runway or bird strikes. Also, mechanical problems such as rotor imbalances can cause microscopic cracks to form on the turbine blades, leading to their failure.

Most flocks of migrating birds fly at very low altitudes.

Indonesian officials said the engine trouble could not have been related to recent volcanic eruptions of Mount Merapi, some 800 miles (1,300 kilometers) to the east - a view corroborated by Voss.

"It's extremely unlikely this could have had anything to do with the volcanic eruption, but everything ... will be looked at very closely during the investigation," Voss said.

Parts of the engine and its cover fell on the thickly populated western Indonesian island of Batam, near Singapore, but no injuries were reported. Residents there helped authorities pick up more than 100 pieces of debris - mostly small, torn metal but some the size of doors - that were brought to police headquarters.

Airbus has delivered a total of 37 A380s so far. Thirteen are in service with Emirates, 11 with Singapore Airlines, six with Qantas, four with Air France and three with Lufthansa.

Emirates airlines said all of its A380s are flying as scheduled, noting its planes aren't powered by Rolls-Royce engines.

In September 2009, a Singapore Airlines A380 was forced to turn around and head back to Paris after an engine malfunction. On March 31, a Qantas A380 with 244 people on board burst two tires on landing in Sydney after a flight from Singapore.

Last August, a Lufthansa crew shut down one of the engines as a precaution before landing at Frankfurt on a flight from Japan, after receiving confusing information on a cockpit indicator.

Qantas' safety record is enviable among major airlines, with no fatal crashes since it introduced jet-powered planes in the late 1950s.

The first inkling of trouble came about 15 minutes into the flight.

"We were halfway up in the air. Then we heard a bang. Five seconds later, we heard an increased, louder sound. Some people thought it was an explosion. Then we saw smoke," said Hewitt, who was sitting by the window in 52H on the right side on the upper deck.

He walked over to the other side to take a picture and video of the left wing, which showed a rip on the upper surface.

"At this point people were obviously scared. Four babies were crying in symphony," he said.

The captain came on the public address system to explain that one engine was lost and that the aircraft would return to Singapore after dumping fuel, which took more than an hour.

Initially, some people were crying, some swore and some appeared shocked, Hewitt said. But most people stayed calm. One joked by asking a friend "Are we there yet?" Another said "as long as the wing hasn't fallen off."

Hewitt sent a text message to his girlfriend, Hayley Collins, a newspaper reporter: "Hey babe not to alarm you but engine on the A380 I got back on from Singapore to Sydney has blown up mid-flight and torn a hole in the wing. Apparently we're safe and dumping fuel."

Hewitt said the 95 minutes between the first bang and the landing passed quickly as he watched a channel on his seat screen that was broadcasting video from a camera mounted on the plane's tail.

Food service was suspended, but the crew served drinks on request, and people were allowed to go to the toilet. When the plane landed, passengers applauded while a flight attendant made the usual welcoming announcement.

Amateur video obtained from a passenger by AP Television News showed white vapor coming out of the wing as the A380 landed.

It was only when the passengers saw the damage after landing that they realized how serious the situation was.

"I certainly think it was worse than it came across to us. We were sheltered," Hewitt told The Associated Press.

Other passengers echoed his comments.

"You realize when you see it. We were really lucky," said Jean Cook, a retiree on her way from London to New Zealand for a vacation.

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